CMMC vs NIST SP 800-171: Understanding the key differences and overlaps

Both the Cybersecurity Maturity Model Certification (CMMC) and NIST Special Publication (SP) 800-171 play critical roles in strengthening data protection across the Defense Industrial Base (DIB). While they are closely related, they serve different purposes in the Department of Defense (DoD) cybersecurity ecosystem.

NIST SP 800-171 defines how contractors should protect Controlled Unclassified Information (CUI), while CMMC builds on those same requirements to validate that organizations have implemented them effectively through an external assessment.

In this blog, we’ll break down the key differences and similarities between CMMC and NIST SP 800-171, when each applies, and how organizations can approach compliance for both.

What is the difference between CMMC and NIST SP 800-171?

NIST SP 800-171 and CMMC are closely connected but serve different purposes in the DoD’s cybersecurity ecosystem. NIST SP 800-171 provides the blueprint for how organizations should protect CUI, while CMMC acts as the inspection and certification process that verifies those protections are properly implemented.

NIST SP 800-171 outlines 110 security requirements designed to safeguard CUI within non-federal systems. It focuses on the technical and procedural controls that contractors must apply to meet DFARS obligations. Organizations can typically verify their own compliance through a self-assessment.

CMMC, on the other hand, is a mandatory certification program for DoD contractors. It builds upon NIST SP 800-171 and introduces maturity levels that require independent assessments. While Levels 1 and 2 align with the 110 NIST controls, Level 3 includes additional enhanced practices from NIST SP 800-172 for advanced threat protection.

In short, NIST SP 800-171 tells you what to do, and CMMC ensures you’ve done it correctly through verified certification.

At a glance: The differences between CMMC and NIST SP 800-171

Which one should you choose?

The choice between CMMC and NIST SP 800-171 depends on the type of information your organization handles and your role within the DIB.

If your organization handles CUI as part of a DoD contract, CMMC Level 2 compliance is required. Since CMMC Level 2 aligns directly with NIST SP 800-171 requirements, achieving NIST SP 800-171 compliance is the foundation for meeting this level.

If your organization handles only FCI and not CUI, CMMC Level 1 compliance is required. This level focuses on safeguarding basic information through 17 fundamental security practices.

Here are some examples that can help clarify which compliance applies:

• Prime contractors and subcontractors that process or store CUI must implement all 110 controls in NIST SP 800-171 to meet CMMC Level 2.

• Vendors or service providers that only handle FCI, such as logistics or basic IT support, typically fall under CMMC Level 1.

• Organizations managing both FCI and CUI need to comply with CMMC Level 2, and potentially higher levels if they support critical national security systems.

• In summary, NIST SP 800-171 defines the security controls, while CMMC determines how compliance with those controls is assessed and certified.

What is CMMC?

CMMC is a cybersecurity certification program developed by the DoD to ensure that contractors and subcontractors in the DIB safeguard FCI and CUI according to required security standards. It builds on NIST SP 800-171 by adding a verification and certification layer that confirms the required controls are properly implemented and maintained.

Any organization that handles FCI or CUI under a DoD contract must achieve the appropriate CMMC level, verified through an independent assessment conducted by a certified third-party assessment organization (C3PAO) authorized by the Cyber AB. 

The certification process can take anywhere from 6 to 12 months, depending on the organization’s readiness, and typically costs between USD 15,000 and USD 100,000, covering preparation, remediation, and audit fees. 

Why is CMMC important?

CMMC plays a critical role in protecting the DoD supply chain by ensuring that every contractor handling FCI or CUI maintains a verified level of cybersecurity maturity. It helps reduce the risk of data breaches, intellectual property theft, and supply chain attacks that could compromise national security.

Beyond meeting regulatory requirements, achieving CMMC certification builds trust with federal agencies and primes contractors for long-term partnerships. It also strengthens internal security practices, helping organizations identify vulnerabilities, standardize processes, and align with broader compliance goals.

What are the three levels of CMMC?

CMMC 2.0 includes three maturity levels designed to match the type of data an organization manages and the strength of security needed to protect it. Level 1 applies to contractors handling only FCI and covers 17 basic practices. Level 2 corresponds to the 110 controls outlined in NIST SP 800-171 for safeguarding CUI. Level 3 is intended for organizations supporting high-priority defense programs and adds enhanced measures drawn from NIST SP 800-172.

Do we need to renew CMMC compliance?

Yes. CMMC certification is not permanent and must be renewed periodically to ensure that contractors maintain the required cybersecurity maturity. Under CMMC 2.0, Level 1 organizations must perform an annual self-assessment and submit results to the Supplier Performance Risk System (SPRS). Level 2 (prioritized) organizations undergo a third-party assessment every three years, while Level 2 (non-prioritized) contractors perform annual self-assessments. Level 3 contractors, supporting high-priority defense programs, require government-led assessments every three years.

These recurring assessments help verify that security practices are consistently implemented and effective, reducing the risk of lapses between audits. Continuous monitoring, documentation updates, and timely remediation of Plan of Action and Milestones (POA&M) items are essential to maintain certification readiness year-round.

Can you automate the CMMC certification process?

While CMMC certification itself cannot be fully automated, several parts of the process can be significantly simplified through automation. Tools that map NIST SP 800-171 and CMMC controls, track evidence collection, and generate compliance reports can help reduce manual effort and human error.

Automation is particularly useful for continuous monitoring, policy updates, and gap analysis, allowing organizations to stay audit-ready throughout the year. By centralizing documentation, tracking POA&M progress, and aligning control implementation with NIST SP 800-171 requirements, automation platforms make compliance faster, more consistent, and easier to manage across teams.

What is NIST SP 800-171?

NIST SP 800-171 is a set of security requirements designed to protect CUI in non-federal systems. It includes 110 requirements across 14 families that form the basis for Level 2.

Organizations that work with the DoD or handle CUI from other federal agencies must follow these requirements. Audits are done through self-assessments, with scores submitted to SPRS. Timelines vary based on readiness but often take a few months, and overall costs depend on scope, internal capacity, and whether external support is involved.

What are the requirements of NIST SP 800-171?

NIST SP 800-171 lays out a clear set of requirements for safeguarding CUI in non-federal systems. These requirements guide how organizations should manage access, protect data, monitor systems, and maintain security across their environment.

The standard includes 110 security requirements organized into 14 families, covering areas like access control, incident response, risk management, and system integrity. These controls form the foundation for CMMC Level 2. Organizations self-assess against these controls, document their compliance in a System Security Plan (SSP), and then calculate and submit their score to the SPRS database.

Is compliance with NIST SP 800-171 mandatory?

Yes, NIST compliance is mandatory for any org that handles CUI for federal contracts. It’s a core requirement built into DFARS clauses, which means contractors must meet the controls in SP 800-171 and report their score in SPRS to remain eligible for awards.

For orgs that don’t work with CUI or don’t fall under DFARS, NIST compliance isn’t required, though many still use it as a best-practice baseline for strengthening security.

Can you automate NIST SP 800-171 compliance?

Yes, you can automate large parts of NIST SP 800-171 compliance, especially tasks like evidence collection, control tracking, gap analysis, and continuous monitoring. Automation tools reduce manual effort, surface noncompliant controls early, and maintain updated documentation that aligns with SP 800-171 and DFARS needs.

That said, automation can’t replace core responsibilities like implementing technical safeguards, conducting internal reviews, or making risk-based decisions. It accelerates compliance, but human judgment is still required to validate controls and prepare for assessments.

What are the similarities between CMMC and NIST SP 800-171?

CMMC and NIST SP 800-171 share a strong foundation because both are built to protect the same type of data and use many of the same technical expectations. Both require organizations to implement security controls that safeguard FCI or CUI, maintain documented processes, track remediation activities, and demonstrate ongoing compliance rather than one-time readiness. They also rely on structured assessments where controls are evaluated for design and effectiveness.

A major similarity is that CMMC Level 2 is directly aligned with the 110 SP 800-171 controls. The DoD intentionally designed Level 2 around these requirements, which means organizations following SP 800-171 are already meeting most of the underlying expectations for Level 2. Official mappings between the two exist in DoD and NIST documentation, allowing teams to trace each practice and understand how compliance with one supports compliance with the other.

How Scrut simplifies both CMMC and NIST SP 800-171 compliance

Scrut brings all your controls, evidence, and assessments into one place so you can manage CMMC and NIST SP 800-171 without juggling spreadsheets or manual trackers. You can map controls across both standards, automate evidence collection, monitor gaps in real time, and use pre-built templates aligned with DoD and NIST requirements.

The platform also streamlines assessments through automated workflows, alerts, and auditor-ready reports that reduce preparation time. Whether you are pursuing CMMC certification or maintaining SP 800-171 posture for DoD eligibility, Scrut helps you stay compliant with less effort and complete visibility. Book a demo today to learn more.

FAQs

Can I get CMMC certified without first meeting NIST SP 800-171?

No. CMMC Level 2 is built on the 110 security requirements in NIST SP 800-171, so you must meet those practices before you can be certified.

Is NIST SP 800-171 Rev. 3 now required for CMMC?

Not yet. CMMC is still aligned with NIST SP 800-171 Rev. 2. Rev. 3 is expected to influence future updates, but it is not part of the current rule.

Do MSPs need to be Level 2 certified themselves?

Only if the MSP directly handles, stores, or processes CUI. If they only support the environment without accessing CUI, they typically fall under Level 1 or may not require certification.

Can I combine NIST SP 800-171 and CMMC implementation into one project?

Yes. Because Level 2 mirrors NIST SP 800-171 practices, organizations can implement both together by building the controls once and applying them to both requirements.

Can you replace NIST SP 800-171 with CMMC?

No. NIST SP 800-171 defines the security requirements, while CMMC is the certification model that verifies implementation. You need both if you handle CUI for DoD contracts.